This is a copy of the original John Linsley-Hood article that appeared in Wireless World in 1969. This design, almost 50 years old, is still built in its hundreds all over the world. A quick root around on the web will show numerous kits, many of quite acceptable quality, emanating from China and Hong Kong. Its enduring appeal is its elegant simplicity arising from the use of only 4 transistors in its most basic form and sweet, organic sound. Modern versions replace the old, slow transistors with more recent equivalents which have given it a new lease of life.
It does not deal with low impedance speaker loads very well, and one has to make adjustments to some resistor values to tailor the amplifier to the speaker load (i.e. 4, 8 or 16 Ohms). Nevertheless, this is still one of the most iconic amplifier designs ever produced.
In 1996, JLH wrote a short article in Wireless World about the amplifier, putting the design in context and how it related to the Williamson tube amplifier